Ionization devices are well known for use in enhancing environments in which human activities take place, for example, in reducing the uncomfortable effects of a highly pollenated atmosphere or an atmosphere which contains too few negative ions and a surplus of positive ions. Breathing in an excess proportion of positive ions tends to lower the oxygen level of the blood and increases the accumulation of serotonin (HT-5) a neuro-hormone that induces sleepiness, depression, irritability, respiratory ailments and headaches. Inhalation of negative ions increases the body's ability to absorb and utilize oxygen and reduces the level of serotonin, thus eliminating all the ill-effects of the positive ions. Such inhalation is known to produce an uplifting effect as well as to increase a person's general sense of wellbeing.
Conventional ionization devices, hereinafter termed ionization devices of the kind specified, comprise an ionization electrode, and means for coupling the electrode to a source of high voltage. The ionization electrode is typically in the form of a conductive needle or a very fine wire. To produce negative ions, air particles in the vicinity of a negative ionization electrode are ionized by electrons provided by the electrode.
Conventionally, shields are provided in coaxial peripheral spaced disposition with respect to the ionization electrode for preventing accidental direct contact with the needle which could result in significant injury due to the high voltage involved. Spurious contact between the high voltage electrode and various objects such as clothing or furniture can also cause damage to the needle.
One conventional type of ionization device employs a generally tubular shield arranged coaxially about the ionization electrode and formed of insulative material. The presence of such a shield results in the following drawback: Ions of the same sign as those being produced at the electrode tend to build up along the surfaces of the shield. The build-up of these ions can result in the establishment of an electrostatic field which inhibits the creation of such ions at the electrode and thus gradually reduces the ion-producing efficiency of the electrode.
There is also produced a further repulsive electric field generated by the ion cloud present in the immediate vicinity of the electrode and identically charged to the ions being produced thereby. This additionally impedes ion production.
A second type of conventional ionization device employs a tubular shield formed of conductive material connected to ground, and disposed in coaxial spaced relationship with respect to the ionization electrode. The use of a conductive shield involves the risk of electrical arcing from the ionization electrode to the grounded shield in the event of momentary shortening of the electrical path between the shield and the electrode due to the presence of spurious material therebetween.
A further difficulty in the use of conductive grounded shields is that ions produced by the ionization electrode tend to migrate to the grounded shield instead of becoming dispersed in the atmosphere as desired.
U.S. Pat. No. 3,234,432 shows an air ionizer comprising a sheet metal shield electrode and a fine wire electrode. The shield electrode is coupled to ground across a resistance in the megaohm range and provides a path of controlled leakage of ions during normal operation thus providing a relatively proportional flow of ions to the shield electrode and an easily controlled flow of ions for application to a subject. U.S. Pat. Nos. 3,783,283 and 3,396,308 both relate to the use of ionization in electro-photography. The former patent shows a grounded semi-conductor shield for use in association with an ionization electrode. The latter patent shows a conductive housing having dielectric strips between the housing and the ionization electrode which are coupled to ground across a very high resistance. According to an alternative embodiment shown in the latter patent the housing is made of a dielectric material and conductive strips are interposed between the housing and the ionization electrode.
The present invention seeks to overcome the disadvangages of prior art ionization devices and provides a device constructed to have a housing or shield in the vicinity of the ionization electrode and having an ion distribution efficiency at least as great as that of a device in which no housing or shield is disposed in the vicinity of the ionization electrode.
A further significant limitation in conventional ionization devices is that the range of effectiveness of such devices is limited to approximately 3 to 4 meters from the ionization electrode. It is often desired to distribute negative ions in a relatively large open or closed volume such as in a factory, airplane or meeting hall. In order to achieve these objectives with conventional ionization devices, it is necessary to provide a number of such devices and to distribute them over the volume, the distribution arrangement being dictated by the effective range of each device. This involves a relatively high cost due to the fact that each conventional device is provided with its own separate power supply and thus relatively bulky units are required and significant cost is involved.